That is one takeaway from a road test of the automaker's ProPilot 2.0 technology as the industry scrambles to deliver self-driving vehicles.

Nissan's semi-autonomous driving package promises no-hands, auto-navigating highway driving from on-ramp to off-ramp, automatically passing cars along the way. The system goes on sale in Japan this year but won't arrive in the U.S. for some time.

The 2.0 system makes several advances over the first-generation ProPilot that Nissan introduced in 2016. Chief among them is real hands-off driving and automated lane changing. The old system doesn't allow either, or take orders from the navigation system to drive to a destination.

For much of a test drive here in the foothills of Mount Fuji, the new-generation ProPilot did all this.

As the car moved along, I had the freedom to jot down observations in my reporter's notebook, take photos or just enjoy the scenery. The car expertly drove itself around every bend in the road, interrupting with an occasional warning for me to keep my eyes and attention front and center.

It changed lanes by itself around slower trucks and highway interchanges. While the car switches lanes, however, a driver must still keep a light touch on the wheel as a safeguard.

Speed trap

But there also was some aggravation that reflects the state of the industry's development in this emerging technology.

If a driver accelerates beyond the posted speed limit by more than 10 km an hour (6 mph), the no-hands function automatically shuts off. That requires regrasping the steering wheel to satisfy the robotic system.

For drivers who want to go faster, that is a major irritant.

Throughout my drive, the posted speed limit never topped 80 km an hour (50 mph), even though the traffic around me clipped along at more than 60 mph — even in law-abiding Japan. ProPilot kept beeping at me to "Look Forward!" Yet all I could see was a blur of cars zooming past.

In cases where I came up behind a slower car, passing was nearly impossible. ProPilot 2.0 has automated passing ability, but it was usually stymied by the rush of cars overtaking me from behind.

A ProPilot 2.0 sensor in the vehicle, below, monitors the driver, above, to ensure attention is on the road.

Worse still, the posted speed limit often changed during my two-hour drive, dropping to just 50 km an hour (31 mph) in one stretch. To ProPilot's credit, my car's speed automatically fell in sync — score one for technological precision. But it forced me to continue hands-free driving at a dangerously slow pace or take the wheel myself if I wanted to go faster.

The constant switching back and forth became such a hassle that I ended up just driving myself.

Fortunately, when hands-off driving is unavailable, the basic ProPilot function — the one already on the market — kicks in. That system requires you to hold the wheel, but it keeps the car nicely centered in the lane.

In Japan, ProPilot 2.0 is being offered standard in all hybrid versions of the Nissan Skyline, the upscale sedan sold as the Infiniti Q50 in the U.S. and other markets. The traditional gasoline versions of the Skyline don't offer ProPilot 2.0, even as an option. That is because the Skyline's hybrid system has safety redundancies built into the system that are required for ProPilot's automated braking and steering, said chief engineer Shigetoshi Tokuoka.

Nissan concluded it wasn't worth the extra cost of adding the systems to the gasoline variants.

U.S. outlook

The biggest hurdle to Nissan bringing the enhanced 2.0 system to the U.S. is mapping.

The system relies on 3D, high-definition highway maps for centimeter-level precision. That mapping is more easily done in compact Japan than in expansive North America.

Nissan is preparing to launch ProPilot 2.0 in the U.S., but it won't be introduced on an Infiniti nameplate, said Tokuoka, who oversees the Infiniti Q50 and Q70 sedans as well as the Q60 coupe.

Tokuoka declined to say which nameplate would get it or when.

But he added that the technology is being timed for the introduction of a new model. He wouldn't clarify whether that means a new product or a revision of an existing nameplate.

Meanwhile, Nissan's U.S. tech center is testing ProPilot 2.0 for local needs, according to Chris Reed, r&d chief for North America. The effort requires millions of miles of validation on U.S. roads to capture unique regional driving conditions, he said.

But ProPilot 2.0 still faces limitations, even in Japan.

The hands-off function can be used only on divided highways that have been mapped in 3D high definition. It can't be used in complicated expressway interchanges, tight curves, toll booths, tunnels or construction areas. Hands-free driving also won't work when it is raining hard enough to require the wipers to operate.

But Tokuoka said hands-free mode is meant to alleviate the stress of driving long hauls or to lighten the load of leisurely trips, not to power people through their hectic morning commutes.

"If you want to drive yourself, you can," he said. "If you want to relax and have the car assist you, you can do that, too — like when you're tired after coming home from golf."

Given that caveat, ProPilot 2.0 performs as advertised, as long as you're not in a rush.

Nissan announced plans in 2013 to have multiple autonomous vehicles on the market by 2020. The Japanese automaker later fine-tuned the plan, saying a multilane highway system would debut around 2018 and that a system capable of handling urban intersections would arrive around 2020.

Autonomous driving is now a key pillar of Nissan's so-called Intelligent Mobility product development strategy, which focuses on electrification, autonomy and connectivity.

Nissan CEO Hiroto Saikawa said in May he wants annual sales of vehicles with ProPilot semi-autonomous driving systems to reach 1 million units in the next four years.

Nissan plans to be selling that technology in 20 nameplates in 20 markets.